1. Field of the Invention
The present invention relates to a projection-type display apparatus that irradiates an image formed on a light valve with illumination light, and magnifies and projects the image on a screen using a projection lens, and in particular relates to a projection-type display apparatus for stereoscopic display.
2. Description of Related Art
JP 2005-65055A, for example, discloses that a video display apparatus for stereoscopic display is composed of one projection-type display apparatus that uses liquid crystal panels for light valves, aiming to make the apparatus small and easy to be installed, and enabling stable stereoscopic display images to be obtained. This conventional projection-type display apparatus is shown in FIG. 11.
An optical system 100 that forms blue, green, and red light images is constituted by a light source lamp 101, dichroic mirrors 102 and 103 for color separation, reflection mirrors 104 to 106, and liquid crystal panels 107r, 107g, and 107b for image formation. Blue, green, and red light beams from the liquid crystal panels 107r, 107g, and 107b are combined by a combining prism 108, and the combined light is projected using a projection lens 110 via polarization rotation liquid crystal 109. The polarization rotation liquid crystal 109 switches the polarization direction of the projection light between 0° and 90°.
Blue, green, and red light beams for the right eye and for the left eye are emitted alternately from the optical system 100 for each field. At this time, the timing for emitting the green light for the right eye and for the left eye is shifted by one field relative to the timing for emitting the red and blue light for the right eye and for the left eye. Furthermore, the polarization direction of the projected light from the combining prism 108 is switched between 0° and 90° for each field by the polarization rotation liquid crystal 109. Accordingly, stereoscopic images can be viewed using polarization glasses.
In order to control polarization at a high speed, OCB mode liquid crystal whose response speed is about 5 msec, ferroelectric liquid crystal having high-speed response on the order of microseconds, or the like is used as the polarization rotation liquid crystal 109. With this configuration, it is possible to display stereoscopic video with little flicker, using one small projection-type display apparatus for displaying projection images, for which installation adjustment is easy.
However, since an image for the right eye and an image for the left eye are formed and switched for each field, cross talk occurs, that is, the image for the right eye enters the left eye, and the image for the left eye enters the right eye. Significant cross talk results in a double image. Further, since an image for the right eye and an image for the left eye are switched by time division, a slow switching speed causes flicker to occur. In order to eliminate crosstalk and flicker, the high-speed response is necessary not only for liquid crystal cells for polarization control, but also for liquid crystal light valves for image formation.
The response of a liquid crystal light valve necessary for high definition, high quality image display is no more than 8 msec for each tone, and desirably a liquid crystal light valve has a response of 5 msec or less. A practical liquid crystal light valve used in a projection-type display apparatus is constituted from TN mode liquid crystal or VA mode liquid crystal, whose response speed is 10 msec or more. Therefore, it has been difficult to secure a response of 5 msec or less with such a liquid crystal light valve.